This extract is from Grounding for the metaphysics of morals by Kant and is about hypothetical and categorical imperatives. Key information has been highlighted in bold. The numbers in brackets after some paragraphs refer to the explanatory notes below.
All imperatives command either hypothetically or categorically. The former expresses the practical necessity of some possible action as a means to achieving something else that one does or might want. An imperative would be categorical if it represented an action as being objectively necessary in itself without regard to any other end.
Since every practical law represents some possible action as good, and thus as necessary for anyone whose conduct is governed by reason, what every imperative does is to specify some action that is necessary according to the principle of a will that has something good about it.
If the action would be good only as a means to something else, the imperative is hypothetical; but if the action is thought of as good in itself and hence as necessary in a will that conforms to reason, which it has as its principle, the imperative is categorical. (1)
The imperative thus says of some action I could perform that it would be good, and puts the practical rule into a relationship with my will; and it is no less an imperative if I don’t immediately perform the commanded an action simply because it is good – because I don’t know that it is good, and/or because I do know this but my conduct is guided by other maxims that are opposed to the objective principles of practical reason.
A hypothetical imperative merely says that the action is good for some purpose that one could have or that one actually does have. In the former case it is a problematic practical principle, in the latter it is an assertoric one. The categorical imperative, which declares the action to be objectively necessary without referring to any end in view... holds as an apodictic practical principle.
Anything that could come about through the powers of some rational being could be an end or goal or purpose for some will or other. So there are countless possible ends, and therefore there are countless hypothetical imperatives, i.e. principles of action thought of as necessary to attain a possible end in view. Every science has a practical segment in which some purpose is set forth as a problem, and imperatives are offered saying how that purpose can be achieved.
So we can give these imperatives the general label ‘imperatives of skill’. The practical part of a science is concerned only with what must be done to achieve a certain purpose; it doesn’t address the question of whether the purpose is reasonable and good. The instructions to a physician for how to make his patient thoroughly healthy, and to a poisoner for how to bring certain death to his victim, are of equal value in that each serves perfectly to achieve the intended purpose.…